Heat sink for a ferrite material employing metal oxides as the dielectric material



Aprll 12, 1966 H. w. WICHERT 3,245,262

HEAT SINK FOR A FERRITE MATERIAL EMPLOYING METAL OXIDES AS THEDIELECTRIC MATERIAL Flled May 22, 1963 2 Sheets-Sheet l yaw/0110111011llllllll/l/II/M INVENTOR Hans Walter Wichert ATTORNEYS Apnl 12, 1966 H.w. WICHERT 3,246,262

HEAT SINK FOR A FERRITE MA RIAL EMPLOYING METAL OXIDES AS THE DIELE I0MATERIAL 2 Sheets-Sheet 2 Filed May 22, 1963 FIG.6.

PIC-3.5.

WAVEGUIDE FOR Y-CIRCULATOR INVENTOR Hans Walter Wichert ATTORNEYS UnitedStates Patent 8 Claims. 61. ass-1.1

The present invention relates generally .to ferrite devices and, moreparticularly, to a broadband arrangement for conducting heat away from apro-magnetized microwave ferrite, wherein the ferrite is not in directheat-conducting contact or relationship with the Wall of a surroundinghollow conductor.

It has been found that considerable difiiculties are encountered whenheat is to be removed from ferrite elements or structural pieces in themicrowave art if the power is greater than approximately one kilowatt.In known arrangements of this type, the heat is generally given off tothe cooler surroundings by means of convection. In the case of largeheat losses, however, this is possible only to a very limited extent. Inorder that the heat which'is produced nevertheless be carried off, theshape and arrangement of the ferrite, in such microwave structures up tonow, has been so selected that the heat which is produced is carried offby means of direct heat contact with the metallic conductor. This,however, means that at the same time the optimal electrical dimensioningof the ferrite structure must be sacrificed. In ferrite arrangements inwhich, due to special electrical characteristics, there may not be anydirect contact with the metallic hollow conductor, it is therefore notpossible, when the device is operating at high power, to drain the heatoff the ferrite, i.e., it is difficult to remove the heat which isproduced.

There also exists an arrangement in which a liquid coolant surrounds theferrite body and is used for draining off the heat losses of theferrite. The dielectric coolant is continuously circulated by a pumpsystem. However, the expenses of such an arrangement are inherently veryhigh.

With these defects of the prior art in mind, it is a main object of thepresent invention to provide a broadband arrangement which overcomes theabove drawbacks without adversely affecting the electricalcharacteristics of the microwave arrangement.

Another object of the invention is to provide an arrangement forremoving heat from ferrites which is simple and inexpensive.

These objects and others ancillary thereto are accomplished according topreferred embodiments of the present invention wherein an arrangementfor draining the heat off a pre-magnetized microwave ferrite isprovided. In this arrangement there is direct heat exchange contact withthe wall of the hollow conductor. Between the ferrite and the hollowconductor a dielectric is arranged which itself is a good conductor ofheat.

The interposition of a suitable dielectric between the ferrite and thehollow conductor has but little influence on the electricalcharacteristics of such a microwave structure, While there is asubstantial improvement in the removal of the heat losses of theferrite, i.e., the dielectric which itself is a good conductor of heatwill substantially improve the way in which the heat losses are givenoff to the cooler surroundings of the hollow conductor.

The dielectric material can, for example, be the oxides of beryllium,aluminum or magnesium inasmuch as these materials, in addition to havinga low dieiectric loss in a microwave region, are very good conductors ofheat and have a thermal conductivity which is approximately in the sameorder of magnitude as the thermal conductivity of the correspondingmetals. The dielectric materials at the same time serve for holding orpositioning the ferrite part within the hollow conductor and maintainthe ferrite element at a predetermined spaced distance from the wall ofthe hollow conductor.

In order that the dielectric material may conduct the heat which isproduced to the cooler hollow conductor as quickly as possible, it isexpedient that the dielectric material touch the ferrite on two oppositesurfaces and itself be in contact with the wall of the hollow conductorover as large a contact surface as possible. It is also possible tosurround the ferrite elment on all sides with this dielectric materialwhich itself is in engagement with the respective hollow conductor wall.According to a further feature of the present invention the ferrite canbe equipped with at least one bore in which there is a core of theabove-mentioned dielectric material, this core being connected to thehollow conductor of the arrange ment.

Additional objects and advantages of the present invention will becomeapparent upon consideration of the following description when taken inconjunction with the accompanying drawings in which:

FIGURE 1 is a cross-sectional View through a first embodiment of thepresent invention with a rectangular wave guide.

FIGURE 2 is a cross-sectional view through a second embodiment whereinthe elements are circular in cross section.

FIGURE 3 is a cross-sectional view of a modification of the embodimentof FIGURE 2.

FIGURE 4 is a cross-sectional view of a third embodiment for aY-circulator.

FIGURE 5 is a cross-sectional view of a modification of the embodimentof FIGURE 4.

FIGURE 6 is a cross-sectional view of a fourth embodiment wherein aplurality of ferrite bodies are used.

FIGURE 7 is a cross-sectional view of a modification of the embodimentof FIGURE 6.

With more particular reference to the drawings, FIG- URE 1 illustrates arectangular hollow conductor 1 in which a ferrite 2 is arranged. Inorder to remove the heat produced in the ferrite and for simultaneouslyholding or mounting the ferrite, by sticking a piece of dielectricmaterial 3 is provided which, for example, is made of beryllium oxideand is arranged between the ferrite and the hollow conductor.

As shown in FIGURE 2, in order to drain off the deleterious heat losspresent in the ferrite and to bring this heat loss to the coolersurroundings, the ferrite body 22 may have a bore 20 in which a coremade of the dielectric material 23 which is a good conductor of heat mybe disposed. This material 23 is in good surface-to-surface contact withthe wall of the hollow conductor.

Another form of the invention is shown in FIGURE 3. Arranged within thehollow conductor branching (not shown) is a pre-magnetized hollowferrite 32 having a bore 30. The space between the ferrite and thehollow conductor wall is, in this embodiment, at least partiallyoccupied by the dielectric material 34. The ferrite bore 30 containsdielectric material 33.

The present invention can be used to advantage in Y- circulators, which,in the microwave region, are made up of hollow conductors and possess apre-magnetized ferrite. In order to obtain a large bandwidth for such acirculator, it has already been suggested to provide the ferrite with across section which is approximately the shape of a three-leaf clover.With this arrangement, too,

it is possible to use the above-described dielectric material fordraining off the heat so that such Y-circulators can be used inconnection with substantially greater power.

FIGURE 4 shows such a Y circulator having a suitably cross-sectionedfern'te'42, which is surrounded on all sides by the dielectric material43 so that the crosssectional configuration of the arrangement is atriangle.

In lieu of the cross-sectional configuration of the ferrite shown inFIGURE 4, which is difiicult in practice to produce, the arrangement canbe made as shown in FIGURE 5. Here a ferrite body 52 which has atriangular cross section and a-central longitudinal bore 50 is used. Thecore 53 of dielectric material of good conducting characteristics isinserted into bore 50.

7 FIGURE -6 shows a further embodiment of the present invention in whichthree cylindrical ferrite bodies 62 are positioned together in suchamanner that they mutually'touch each other. The hollow space whichremains in the center between the three ferrite cylinders is, forpurposes of draining oifthe deleterious heat losses,

' filled with a suitably configured dielectric material 63.

FIGURE 7 shows an embodiment of the invention in which the longitudinalbore-70 of the ferrite body' 72,

shown in FIGURE 5, has a triangular cross section.

Again, the bore is filled with the dielectriccore 73 which is in goodsurface-to-surface contact with the wall ofthe hollow conductor of theY-circular. If a good deal of heat hasto be drainedoff, it is furtherpossible to provide additional dielectric material between one ormoreconduction of. the heat losses, andalso the retention of the usualelectrical characteristics, a substantially greater bandwidth,1about40%, than was the case in heretofore known Y-circulat-ors. The reasonfor this might be that,

Ldue .to the central bore in the ferrite, the disturbinginherent'resonances' are shifted out of'the operating region.

'Intorder'that the above-described ferrite arrangements be asindependent of temperature fluctuations as possible, the invention canbe carried further by building up the ferrite bodyof individual'ferrite'layers,*between which there are arranged suitably'configured discs madeof the dielectric material which is a good conductor of heat.

It will be understood that the above description of the presentinventionis susceptible to variousmodifications, changes, andadaptations, and thesame are intended to be comprehended within themeaning and range of equivalents of the appended claims.

What is claimed is: 1. In a broadband arrangement for removing heat in apre-magnetized microwave ferrite in a hollow conduc tor but which is notindirect and heat exchange contact with the wall of the conductor, theimprovement comprising a dielectric material which is a good conductorof heat interposed between the ferrite and the hollow conductor, thedielectric material surrounding the ferrite on all sides, and thedielectric material being one selected from the group'consisting ofberyllium oxide, aluminum oxide, and magnesium oxide.

2. The improvement as defined in claim 1 wherein the ferrite has atleast one opening defined-therethrough which is filled with thedielectric material.

3. The improvement as defined in claim 2 wherein the ferrite is used fora Y-circulator and is triangular in cross section,.said openingextending longitudinally through the ferrite and being triangular incross section.

4. The improvement as defined in claim 2 wherein the cross sections ofthe dielectric material and theferrite are circular.

5. The improvement as defined in claim 2 wherein the ferrite is clovershaped in cross section.

6. In aubroadband arrangement for removing heat in a pre-magnetizedmicrowave'ferrite in aholl-ow'conductor butwhich is not in direct andheat exchange contact with the wall of the conductor, theimprovement'com-prising a dielectric materialwhich is a good conductorof heat interposed between the'ferrite'and the hollow conductor, and aplurality of ferritesbeing'used and defining an opening which is filledwith the dielectric material.

7. The improvement as defined in claim 6'wherein the ferrites arecircular in cross section.

8. In a broadband arrangement forremoving'heat' in a pre-rnagnetizedmicrowave ferrite in a'hollow conductor but which is 'notindirect and"heat-exchange contact with the wall of the-conductor, the improvementcompris ing a dielectric materal 'whch is a good conductor of heatinterposed between the ferrite and thehollow'con- -ductor, said ferrite'being'used for a -Y-circulator and 1 being triangular incross==sec'tion, said'ferrite having at least one opening defined'therethrough which extends longitudinally through the ferrite and istriangular in cross section and "which-is filled with the dielectricChait et al.: New Micr'owave Circulators, Electronics,

Dec. 18, l959, pages 81-83 relied upon.

Lax et al.: Microwave Ferrites and Ferrimagnetics, Lincoln Lab.Publication, McGraw-Hill, received'Sci. Library, Jan. 7, 1962, pages620-623 relied on.

HERMAN KARL SAALBACH, Primary Examiner, ELI LIEBERMAN, Examiner,

1. IN A BROADBAND ARRANGEMENT FOR REMOVING HEAT IN A PRE-MAGNETIZEDMICROWAVE FERRITE IN A HOLLOW CONDUCTOR BUT WHICH IS NOT IN DIRECT ANDHEAT EXCHANGE CONTACT WITH THE WALL OF THE CONDUCTOR, THE IMPROVEMENTCOMPRISING A DIELECTRIC MATERIAL WHICH IS A GOOD CONDUCTOR OF HEATINTERPOSED BETWEEN THE FERRITE AND THE HOLLOW CONDUCTOR, THE DIELECTRICMATERIAL SURROUNDING THE FERRITE ON ALL SIDES, AND THE DIELECTRICMATERIAL BEING ONE SELECTED FROM THE GROUP CONSISTING OF BERYLLIUMOXIDE, ALUMINUM OXIDE, AND MAGNESIUM OXIDE.